Healthy Soil 101: Hard to create, easy to destroy

Fertile topsoil is a lively ecosystem, teeming with microorganisms and worm life. It has robust soil structure that retains water well and allows plant roots to penetrate, to breathe, and to forage for nutrients.

But there’s a problem. We’re running through our supply of fecund soil in the U.S. at an alarming rate, with an estimated 996 metric tons of soil erosion annually. Conventional agriculture enables—and the tight margins of the farming industry incentivize—short-term bounty to the detriment of sustainable practices. Annual tilling, monocropping, and chemical inputs promote an abundant harvest in the near term but ultimately catalyze soil degradation, cause the atmospheric release of stored nitrogen and carbon, compromise the soil structure, decrease water retention capacity, destroy the delicate microbial ecosystem, and make minced meat of the worms. Fostering healthy soil requires playing the long game.

A recent report by the Nature Conservancy estimates that the societal and environmental costs of soil degradation and loss come to about $85 billion per year in the United States. These costs include the unintended negative consequences of conventional farming, ranging from loss of long-term productivity and biodiversity to increased greenhouse gas emissions. As the Nobel Foundation’s Bill Buckner explains,“[Soil health] took a backseat to plant science when the green revolution happened.” But as the pain points of water scarcity and the rising costs of herbicides and pesticides become increasingly acute, soil science is moving to center stage.

“Your ideal topsoil is what we call the A horizon—that’s the one that has a lot of organic matter, microbes, and nutrients. Unfortunately, when we talk about soil loss, it is usually that A horizon,” soil scientist Katy Brantley told FoodFutureCo. “So, we are now working with B horizon soil, or subsoil. It's still soil, but it's not that top layer where everything was growing and dying and recirculating and where plant roots like to grow. So you have to cultivate that B horizon to make that your new A horizon. Things change, but it takes a really long time.”

How do things change? The standard practices for soil health stewardship includes minimizing tillage, cover cropping, and rotating crops. No-till or conservation tillage methods allow the microbial ecosystem to develop and protect soil structure which is vital for water retention. Cover cropping increases the amount of time during the year that root systems are actively building nutrients in the soil and helps prevent soil from drying out. Rotating crops—especially planting nitrogen-fixing legumes—increases biodiversity, builds soil nutrients, and helps prevent erosion. The Nature Conservancy also estimates that $50 billion dollars of societal and “on-the-farm” value could be recaptured each year through these adaptive soil health management practices.

There is money to be made in good soil. Naturally, in concert with increasing adoption of these traditional methods of cultivating fertile soil, there is a burgeoning industry developing around creative, new ways to contribute to the soil building efforts. Breeding new perennial varietals, surveying the soil microbial landscape and manufacturing biochar make the short list.

Biochar has been hailed as a potentially wunderkind technology to heal agricultural soil in the U.S., which has lost up to 60% of its original organic carbon content. This loss is problematic from both greenhouse gas emission standpoint and from a soil nutrient standpoint. Biochar has been identified as a possible antidote for this trend through its capacity to sequester carbon and increase soil fertility. Though a number of questions about its efficacy and practical application at scale have yet to be conclusively answered, companies are clamoring to corner the biochar market, projected to reach $3.14 billion by 2025.

Biochar is made by burning organic matter (think agricultural waste materials like corn husks) in an extremely low oxygen environment through a process called pyrolysis. The result is a charcoal-esque soil additive that sequesters carbon for the long haul, boosts soil fertility and water retention, and minimizes nutrient run off. Advocates for biochar point to the fact that its benefits are further amplified by its impressive persistence in the field—it outperforms all other organic inputs in terms of staying power.

Close up of threshed Kernza® perennial grain seeds | Image courtesy of The Land Institute

Perennial crops also promote healthy soil through the simple act of staying put. Unlike annual crops, which must be replanted each year—often with the assistance of tilling and herbicides—perennials don’t have to be established in the field year after year, leaving root systems intact and minimizing soil disruption. According to The Land Institute, 85% of human food is grown from annual crops, but they’re working to shift that ratio by domesticating wild perennials and perennializing domestic crops.

Kernza farmer displaying its long roots next to conventional wheat | Image courtesy of Jim Richardson

The Land Institute’s Kernza® Grain, a domesticated perennial wheatgrass with roots that can reach over ten feet below the soil surface (twice that of annual wheat), has already hit the market as Long Root Ale from Patagonia Provisions. Select restaurants have incorporated Kernza into their menus, and General Mills’ Cascadian Farms is prepared to incorporate Kernza into their products for sale by late 2019. Meanwhile the Land Institute is also working to perennialize annual crops such as wheat and sorghum by cross breeding them with perennial cousins.

But the importance of the DNA within the soil is now on the radar alongside plant cross breeding and genetics. The startup Trace Genomics, often called the “23andMe” of soil, is sequencing soil sample DNA to offer farmers insight into the microbial composition of their fields. Trace Genomics can help farmers simply identify common pathogens in their soil or can give them a more comprehensive microbial evaluation. Trace Genomics not only aims to help their customers better understand the soil they’re planting in, but is building a database documenting patterns in soil, location, crops, and field treatments.

Better data and a deeper understanding of the ecosystem beneath the soil’s surface will be vital for developing new solutions and for supporting adoption of traditional soil stewardship practices. And though cultivating healthy soil is a notoriously slow process, it’s absolutely doable. Amidst the groundswell of energy for innovation, data, and tech-driven solutions, the underlying principles are age-old and simple. As Professor and MacArthur Fellow David Montgomery explains, “ditch the plow, cover up, grow diversity.”

In Montgomery’s recently published book, Growing a Revolution, he demonstrates that it is not only possible but also profitable to restore degraded soil through these three farming principals and argues that revitalizing our commercial agricultural land at scale is feasible. With about 40% of the cropland used for cash crops corn, soy, wheat, and cotton now cultivated in no-till or strip-till systems, the needle is starting to move. Soil fertility is a topic that transcends the conventional-organic labeling divide: restoring our soil is a cause for the whole industry to rally behind with the potential to help combat climate change, reduce water consumption, mitigate reliance on chemical inputs, and increase long term productivity.